docs: def _parse_reference(self, el):
          """Return reference ID from href or text content."""
          if '#' in el.get('href', ''):
              return [el.get('href').split('#', 1)[1]]
          elif 'rid' in el.attrib:
              return [el.attrib['rid']]
          elif 'idref' in el.attrib:
              return [el.attrib['idref']]
          else:
              return [''.join(el.itertext()).strip()]